Udon is one of the wheat flour noodle types characteristic of Japanese cuisine, like soba. The word comes from the South Chinese name for wontons. Udon was borrowed from China in the 14th century, unlike ramen, which made its way to Japan from China after the end of Japan’s isolationist policy at the beginning of the Meiji era. The main difference between udon and ramen is that kansui alkaline solution is not used in udon noodle preparation. The key ingredient in the dish itself is the thickest noodles, ranging from 2 to 4 mm in diameter.